Uploads are accomplished on Orthodox Wiki by using the toolbox link: Upload file. This will take you to the Upload file page on the Orthodox Wiki Commons site. Read the information at the top of that page and then fill out the form at the bottom. Submit the form by clicking the "Upload file" button. (You may need to navigate back to Orthodox Wiki from Orthodox Wiki Commons when you are done.)
Uploaded files are usually image files that an Orthodox Wiki contributor plans to include in an article, but other file types are sometimes uploaded too.